Cough is a mode of transmission of respiratory pathogens and a prominent symptom of severe cough-transmissible respiratory illness (SCTRI), such as influenza, tuberculosis (TB), and pertussis; as well as of other severe pathologies, especially pneumonia. Close contact between infected and uninfected groups, as among healthcare workers (HCWs) and patients can lead to rapid spread of SCTRI within and between the two groups, widespread illness, severe staffing shortages, and even deaths. Organisms are constantly being introduced from the community (by HCWs, visitors, and new patients) with potential transmission to those individuals who are most severely ill and, thus, most vulnerable to SCTRIs. Social isolation strategies used in epidemics are not well-suited for use in patient care. An important ongoing problem is that SCTRI is often not identified in patients or HCWs with cough early enough to prevent transmission to staff and other patients. Moreover, automatic assessment of cough as a vital sign would permit better clinical assessment of pneumonia, particularly in locations that are remote from clinical facilities.
The clinical interpretation of cough has always depended on individual judgment and the skill of the observer. Clinicians are taught to discern cough characteristics to distinguish infectious etiology and severity. Yet, it has been shown that such perception-based judgment has variable intra- and inter-rater reliability. In spite of these problems, the acoustic characteristics of cough have not previously been objectively quantified as the basis for a disease-screening tool or as a vital sign.